feat: enhance ClawdHub integration with paging and retry

Add paging support when loading ClawdHub skills
Retry on API errors and throttle for ClawdHub requests
Load source content on source change and show loading indicators

packages/ui/src/lib/api/types.ts

@@ -828,6 +828,14 @@ export interface SkillsCatalogResponse {
   ok: boolean;
   sources?: SkillsCatalogSource[];
   itemsBySource?: Record<SkillsCatalogSourceId, SkillsCatalogItem[]>;
+  pageInfoBySource?: Record<SkillsCatalogSourceId, { nextCursor?: string | null }>;
+  error?: { kind: string; message: string };
+}
+
+export interface SkillsCatalogSourceResponse {
+  ok: boolean;
+  items?: SkillsCatalogItem[];
+  nextCursor?: string | null;
   error?: { kind: string; message: string };
 }